Rotary blade assembly



March 28, 1961 F. J. MACHOVEC 2,976,566

ROTARY BLADE ASSEMBLY Filed Aug. 5, 1958 INV EN TOR fine-0 J Mac/1o vac ROTARY BLADE ASSEMBLY Fred J. Machovec, 63 N. Merideth Ave., Pasadena, Calif.

Filed Aug. 5, 1958, Ser. No. 753,375 Claims. c1. 56-495 This invention relates to rotary blade assemblies and more particularly to an improved assembly of this type utilizing a specially shaped hub plate to hold a multiplicity of blades in rigidly assembled position on a rotating shaft.

The structure of this invention, while being particularly applicable to power-driven edger blades, has general application to rotary blade structures and particularly to those wherein it may be desirable to replace one of several blades for various reasons. In lawn edging devices, for example, it has been the practice to employ rotary blades to trim foliage along paths, driveways, curbing and the like, under conditions wherein the blade comes in contact with earth, crushed rock, gravel and other hard objects likely to dull or damage the blade. Under these severe operating conditions, the blades become dulled after a short period of use and one or more of the blades may become damaged. In prior edging assemblies it was necessary to replace the entire unit with a new one since it was not feasible for the average user to replace the damaged blade with a new one or to re-use the same hub unit with a different set of blades. Recognizing this shortcoming certain designs have been proposed using a series of interfitting plates and blades having rivets, screws, welding or other fastener means holding the parts together and additional means for holding the assembly to the power-driven shaft.

The present invention provides a unitary structure obviating the shortcomings and disadvantages of prior assemblies and featuring an assembly comprising a single hub plate and a plurality of separate identical blades formed to have interlocking engagement with the hub. Disassembly of the simple fastener means holding the parts assembled to a shaft permits any one or more of the components to be replaced or serviced after which the assembly can be relocked in its operating position on a driving shaft.

Accordingly, it is an object of the present invention to provide an improved rotary blade construction featuring a minimum number of interlocking parts adapted to be held in assembled relation by the means mounting the same on a driving shaft.

Another object of the invention is the provision of a simple plate hub formed to seat and rigidly locate a plurality of blades when the assembly is secured in its operating environment.

Another object of the invention is the provision of an improved lawn edging blade comprising a plurality of strips rotating in a common plane and held rigidly in assembled relation by a one-piece hub plate.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated:

Figure 1 is a perspective view, partly in dot-and-dash line and partly in full line, showing a powered lawn United States Patent 9 i 2,976,666 Patent d Mar. 2 ,19 1

edger having the rotary blade assembly of the present invention mounted thereon;

Figure 2 is a fragmentary sectional view on an en' larged scale taken along line 2--2 on Figure 1;

Figure 3 is a cross-sectional view taken to show the hub plate per se as viewed from the left side of Figure 2; and

Figure 4 is a perspective view of the hub plate.

Referring to the drawings, there is shown a rotary blade assembly designated generally 10 secured by a nut 13 to the outboard end of a power-driven shaft 12 of a power-driven lawn edger shown in dot-and-dash line in Figure 1 and designated generally 11. Edger 11 is supported by suitable wheels 14 and includes a gasoline engine 15 having its drive shaft connected by belt 16 to drive shaft 12. The edger has a propelling handle 17 by which the edger may be guided and a suitable control lever 18 connected by a linkage 19 to engage and disengage belt 16 driving blade assembly 10.

The blade assembly will be best understood by reference to Figures 2 to 4 wherein it is seen to comprise a hub plate 20 and a pair of criss-cross arranged strip blades 23, 24. Plate 20 is preferably formed from sheet stock, as for example, sheet metal or high strength molded plastic. This plate is stamped or otherwise processed to provide a pair of wide shallow channels 21, 22 arranged at right angles to one another and lying in closely spaced parallel planes. As is best shown in Figure 2, the bottom of channel 21 is parallel to the bottom of channel 22 but spaced therefrom by the thickness of one of the blades 23, 24. This permits the outer blade to rest firmly against the adjacent surface of the inner blade and flush with the bottom surface of channel 22 in the manner made clear by Figure 2.

An important feature of the invention is the deformation of'diagonally disposed rim -portions-25, 25 of the hub plate to provide upstanding side walls 26, 26 lying normal to the surface of channels 21, 22 and parallel to the opposite edges of these channels. To be observed is the fact that side walls 26 of each upstanding portion 25 lie at right angles to one another where a single pair of strip blades are employed. However, these walls will be differently disposed if a larger number of blades are employed, as may be the case for certain applications. It is pointed out that walls 26 are co-extensive with the side walls of channels 21 and 22 and cooperate therewith in holding blades 23 and 24 firmly anchored against rotary displacement relative to one another and I hub plate 20.

Each of blades 23, 24 as well as the hub plate is pro vided with a centrally disposed opening 28 for receiving the threaded trunnion 29 on the outer end of driven shaft 12. The three elements comprising the assembly are inserted over trunnion 29 in the order made clear by Figure 2 after which the assembly is firmly and frictionally locked in place thereon by a suitable spring washer 30 and nut 13.

The leading edges of blades 23 and 24 may be sharpened if desired though, for lawn edging purposes, this is not necessary. It will be understood that the blades are preferably formed from tempered steel and the speed of rotation is such that their blunt leading edges are efiective to cut grass, foliage and shrubbery. If any one of the blades should become worn or bent in use, it is a simple matter to remove it for servicing or for replacement with a new blade by removing nut 13, replacing the damaged blade and reassembling the blade unit on shaft 12. It is therefore apparent that the hub plate 20 may be reused indcfinitely, blades 23 and 24 being replaced as necessary.

It will be recognized that the described structure, though illustrated in connection with a lawn edger, has many other uses which will readily suggest themselves to those conversant with the use of rotary blade assemblies, it merely being necessary to employ suitably shaped blades having their midportions shaped and dimensioned to fit snugly in seating channels 21, 22 of the hub plate. While the particular rotary blade assembly herein shown and disclosed in detail is fully capableof attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

I claim:

1. An article of manufacture comprising a one-piece sheet metal stamping for use in anchoring a pair of crisscross blades to a rotary shaft with the blades rigidly supported in the same general plane and with their ends circumferentially spaced, said stamping having only a central opening forreceiving a single threaded fastener, the rim edges of said stamping being ofiset from the plane of said plate to provide aligned shallow wide channels substantially at right angles to one another and sufficiently wide to receive and seat therebetween a pair of flat strip blades, the bottom surface of one channel lying in a plane parallel to the surface of the other channel but spaced therefrom by approximately the thickness of one of the blades to be seated therein.

2. A hub assembly member for a pair of sheet metal blades, said assembly member comprising a thin walled stamping having a pair of wide shallow blade-seating channels formed therein and extending transversely of one another, the bottoms of said channels lying in parallel planes offset by the thickness of one of the blades to be seated therein, and the rim edges of said plate having portions projecting from the edge portions of said channels and snugly engageable with the edges of a pair of blades when the latter are present in said channels to hold the blades against relative rotary movement, said stamping having passage means centrally of the crossing portions of said channels for a single fastener operative to hold a pair of blades rigidly clamped in said channels.

3. A rotary blade construction comprising a hub and a plurality of blades detachably anchored thereto, said hub including a plate having a plurality of wide shallow channels intersecting one another with the bottom surfaces thereof lying generally parallel and spaced apart by the thickness of one of said blades, the central portion of said blades having a width corresponding to the width of said channels, the rim portions of said plate projecting from the edge portions of said channels and being snugly engageable with juxtaposed edge portions of said blades to hold the latter against relative rotary movement, and detachable shaft and fastener means comprising the sole means for holding said plate hub and said blades detachably secured together along an axis centrally through said plate hub and normal thereto.

4. A blade construction as defined in claim 3 characterized in that said blades comprise straight strips of substantially uniform width and thickness having one surface of each lying in-a common plane.

5. -A blade construction as defined in claim 3 characterized in that said plate hub is formed from sheet metal and in that the projecting rim portions thereof comprise V-shaped portions of diametrically opposed areas of the rim disposed to provide low height walls lying normal to the plane of said plate hub.

References Cited in the file of this patent UNITED STATES PATENTS 301,375 Lawrence et al. July 1, 1884 799,413 Spencer Sept. 12, 1905 1,404,777 Leutner Jan. 31, 1922 1,725,745 Bauer Aug. 27, 1929 1,744,597 Vasconcellos Jan. 21, 1930 2,515,732 Parry July 18, 1950 2,760,327 Bovee Aug. 28, 1956 2,795,916 Miller June 18, 1957 2,876,027 Sulmonetti Mar. 3, 1959 1 FOREIGN PATENTS 152,399 Australia July 17, 1953 

